I used to do TV repairs and it sounds like it is a common problem. (Is that thing a CRT, a "cathode ray tube" display, just like a conventional TV?) It sounds like a vertical amplifier problem. Fortunately for you, virtually ALL of the vert amp problems I have seen were due to failed solder connections. If you have access to a good electronics tech who can solder real good, you should at least get it looked at for that problem. Look on the main PC board for the vertical amplifier IC. It will have a small aluminum heatsink attached to it. Check the solder connections on all the IC pins. Just resolder them even if you think they are OK. A good solderer can do the soldering in less than a minute. The thermal cycling of turning on & off plus the mechanical vibrations of transport due to the mass of the heatsink can severly stress the solder connections of those IC's. Do that before you jump to any other conclusions. Check the entire printed circuit board for possibly bad solder connections, especially those that get hot, and fix them before you jump. It is standard TV repair proceedure. PM me if you want more help.
